Many devices, such as a turbocharger, use an apparatus to control their functions. For example, pneumatic and electric actuators are used to provide positional control of mechanisms on the turbocharger to adjust and maintain the pressure within the intake manifold of an engine.
FIG. 1 shows a schematic of a system using a turbocharger and an actuator to control boost pressure within the intake manifold 8 of engine 9. The system consists of the vehicle's electronic control unit (ECU) 1, actuator controller 2, actuator 3, turbocharger 4 and turbocharger control mechanism 5. The ECU is connected to the actuator controller by a wire harness 6 having multiple conductors and connectors. The actuator controller is also connected to the actuator by a wire harness 7 having multiple conductors and connectors.
The ECU 1 will provide an electrical signal to the actuator controller 2 that will indicate a desired position of actuator 3. The actuator controller will provide the necessary electrical control to the actuator. The actuator will move the control mechanism 5 of turbocharger 4, to the desired position that will achieve a desired pressure within the intake manifold 8 of engine 9. Actuator 3 also has a means of sensing its position and will feedback this signal to the actuator controller 2. A “closed loop” control scheme is used to maintain a desired actuator position by comparing the feedback value to a desired value and adjusting the control signal, to the actuator, to maintain the position and resulting boost pressure. Other signals, such as an intake manifold pressure-sensing signal may also be monitored, by ECU 1 or actuator controller 2, and used in the “closed loop” scheme to control the intake manifold pressure. The actuator controller can also monitor the performance of the actuator and provide feedback to the ECU. For example, items such as internal actuator temperature, voltage, current, actuator resistance, response time, and number of occurrences of a fault can be monitored and communicated to another system such as the vehicle ECU. Monitoring of some items may be a legislated requirement.
The electric actuator may use a D.C. motor as a means of actuation. The motor may use brushes for commutating its rotating member or it may be a brushless type motor. The brushless motor uses a number of magnetic sensors and an electrical control circuit to commutate its rotor and control its rotation. Magnetic devices, such as Hall effect devices (HED), are commonly used. The HED sensors must be in proximity to the motor's rotor and stator to effectively sense the magnetic field and provide a signal to a control circuit. The brushless motor also has a number of coils, wound with magnet wire, which must be connected to the control circuit. This type of actuator requires a number of electrical connections in addition to the accurate placement of the sensors. Control and connection methods such as separate control circuits may be difficult to assemble, costly, and undesirable. In addition, the motor, HED sensors, and control circuit may not be in one location. For example, the motor and hall sensors may be located in the actuator housing and the control circuit may be in the cover of the housing. This could require a complex interconnection system needing a multiple wire cable that may have durability and reliability issues. The following paragraphs will describe a system that will provide the required control and minimize components and interconnections.